This invention generally relates to magnetic tape cassette storage facilities for digital data processing systems and more specifically to a magnetic tape cassette drive for use in such facilities.
Magnetic tape cassette storage facilities for use in data processing system have become very popular in recent years. This popularity stems from several factors. For example, the cassette is self-contained; thus, it is easier to handle the storage media than in reel-to-reel tape storage facilities. Tape cassettes and their drives are very reliable. Moreover, these facilities are less expensive and more compact than the reel-to-reel tape facilities.
There has been adopted an industry standard for tape cassettes used in digital data processing systems. Thus, drives for these cassettes must also conform to this standard. In one such drive, the corners of the cassette defined by the intersection of the leading and side edges of the cassette engage corner and edge blocks on a frame thereby to locate the cassette in an operating position. In the operating position, magnetic tape in the cassette passes a transducer and an end-of-tape sensor.
In accordance with the foregoing standard the tape contains apertures at predetermined distances from both ends of the tape. Light from a white light source passes through a bottom opening in the cassette into a cavity behind the tape. When one of the apertures passes the sensor, light passes through a corresponding opening in the leading edge of the cassette to a detector. A portion of a housing for the detector interfits this edge opening, thereby to minimize the effects of ambient light changes, especially if the tape flutters away from the sensor. However, ambient light from above the cassette also passes into the cavity. If flutter does occur, ambient light can leak to the detector and produce a false end-of-tape reading.
Moreover, it is difficult to assemble the foregoing tape drive. The transducer and corner and edge blocks individually mount directly to the frame, and their relative positions control the alignment between the transducer and the magnetic tape. They must be positioned accurately. However, the necessary alignment procedures complicate manufacture. Further, it is extremely difficult to replace and align the transducer and edge and corner blocks away from the manufacturing location.
Therefore, it is an object of this invention to provide an improved magnetic tape cassette drive which is less susceptible to the effects of ambient light.
Another object of this invention is to provide a magnetic tape cassette drive in which the end-of-tape sensor is less susceptible to false readings.
Yet another object of this invention is to provide a tape drive in which the transducer alignment procedures are simplified.
Still another object of this invention is to provide a magnetic tape cassette drive in which transducer replacement and alignment procedures are simplified.